Bio-magnetic particles are surface-modified magnetically responsive microspheres which are widely used in immunoassays, gene engineering, cell separation etc. Roy A. Whitehead and Lee Josephson et al provided a process for the preparation of magnetic particles to which a wide variety of molecules might be coupled. The particles comprised ferromagnetic, superparamagnetic or paramagnetic oxides of iron, cobalt or nickel as a metal oxide core, generally surrounded by an adsorptively or covalently bound sheath or coat bearing organic functionalities to which bio-affinity adsorbents might be covalently coupled. Magnetic particles are useful in biological separations in radioimmunoassay, cell isolation, affinity chromatography, immobilized enzyme systems, nucleic acid hybridization, and other biological systems. See U.S. Pat. Nos. 4,554,088, 4,672,040, 4,628,037.
Fluorescence immunoassay (FIA) is also widely used in biotechnology. There are many fluorescent materials that can be used as fluorescent labels, such as organic fluorescent dyes, quantum dots, down-converting rare-earth phosphor nanoparticles and up-converting phosphor nanoparticles etc.
Wang et al provided a process of preparing magnetically responsive fluorescent polymer particles with sizes ranging from 1 to 100 microns. The fluorescent material was used to determine the number of the particles. These polymer particles comprise polymeric core particles coated evenly with a layer of polymer containing magnetically responsive metal oxide as highly sensitive quantitative reagents for biochemical and immunological studies. The surface of these magnetically responsive polymer particles can be coated further with another layer of functionalized polymer. These magnetically responsive fluorescent polymer particles can be used for passive or covalent coupling of biological material such as antigens, antibodies, enzymes or DNA/RNA hybridization and used as solid phase for various types of immunoassay, DNA/RNA hybridization probes assay, affinity purification, cell separation and other medical, diagnostic, and industrial applications. See U.S. Pat. No. 6,013,531.
Chandler et al provided a process of preparing magnetically-responsive fluorescently-tagged particles. These hybrid microspheres are constructed using fluorescent or luminescent microspheres and magnetic nanoparticles. Reactive moieties on the surface of the resultant particles can be used for attachment of biologically active molecules, thus allowing selective separations and analytical assays to be performed. Distinguishable subsets of microspheres can be constructed based on fluorescent intensities, and separations can be affected based on variable degree of magnetic content. Multiple particles populations thus constructed will find utility in a number of fields, including clinical biological assays See U.S. patent application Ser. No. 09/826,960.